subgaleal lipoma

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Subgaleal lipomas are benign adipose-containing tumors that occur between the periosteum and the galeal aponeurosis of the scalp.

Epidemiology

They comprise 2% of all lipomas. They are more common in middle-aged patients and have a male predilection

Clinical presentation

Subgaleal lipomas present as a slow-growing, painless, firm and immobile swelling overlying the frontal scalp.

Pathology

Histology demonstrates mature adipocytes in a connective tissue stroma surrounded by the fibrous capsule, importantly they lack any cellular atypia or mitotic activity.

Radiographic features

Plain radiograph

oval or lens-shaped soft tissue/fatty swelling
smooth convex displacement of the galea aponeurosis

Ultrasound

oval or lens-shaped echogenic swelling
no increased vascularity or cystic features
located between periosteum and galea aponeurosis
smooth convex displacement of the galea aponeurosis
relatively flat base

CT

morphology and anatomical location as above
fat attenuation

MRI

The morphology and anatomical location of the lesion is as above.

T1: hyperintense
STIR: suppressed signal

Differential diagnosis

General imaging differential considerations include:

Practical points

Ideally, the radiology report would comment on the:

size, shape, and location of the lesion
note any vascularity or cystic features